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  • 1
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    The influence of pore-water advection, benthic photosynthesis, and respiration on calcium carbonate dynamics in reef sands (2012)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 57 (3). pp. 809-825.
    Details
    Publikationsdatum: 2016-04-29
    Beschreibung: To investigate diel calcium carbonate (CaCO3) dynamics in permeable coral reef sands, we measured pore-water profiles and fluxes of oxygen (O2), nutrients, pH, calcium (Ca2+), and alkalinity (TA) across the sediment-water interface in sands of different permeability at Heron Reef, Australia. Background flushing rates were high, most likely as a result of infaunal burrow irrigation, but flux chamber stirring enhanced pore-water exchange. Light and pore-water advection fueled high rates of benthic primary production and calcification in sunlit surface sediments. In the light, benthic photosynthesis and calcification induced surface minima in Ca2+ and TA and peaks in pH and O2. Oxygen penetration depth in coarse sands decreased from ∼ 1.2 cm during the day to ∼ 0.6 cm at night. Total oxygen uptake (TOU) in dark chambers was three to fourteen times greater than diffusive uptake and showed a direct effect of pore-water advection. Greater sediment oxygen consumption rates were observed in higher permeability sands. In the dark, TA release was not stimulated by increasing TOU because of a damping effect of pore-water advection on metabolic CaCO3 dissolution efficiency. On a daily basis, CaCO3 undergoes net dissolution in Heron Reef sands. However, pore-water advection can reverse the CaCO3 budget and promote CaCO3 preservation under the most energetic conditions.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lo.2012.57.3.0809
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    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
  • 2
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    Versatile cyanobacteria control the timing and extent of sulfide production in a Proterozoic analog microbial mat (2020)
    In:  EPIC3The ISME Journal, pp. 1-14, ISSN: 1751-7362
    Details
    Publikationsdatum: 2020-09-14
    Beschreibung: Cyanobacterial mats were hotspots of biogeochemical cycling during the Precambrian. However, mechanisms that controlled O2 release by these ecosystems are poorly understood. In an analog to Proterozoic coastal ecosystems, the Frasassi sulfidic springs mats, we studied the regulation of oxygenic and sulfide-driven anoxygenic photosynthesis (OP and AP) in versatile cyanobacteria, and interactions with sulfur reducing bacteria (SRB). Using microsensors and stable isotope probing we found that dissolved organic carbon (DOC) released by OP fuels sulfide production, likely by a specialized SRB population. Increased sulfide fluxes were only stimulated after the cyanobacteria switched from AP to OP. O2 production triggered migration of large sulfur-oxidizing bacteria from the surface to underneath the cyanobacterial layer. The resultant sulfide shield tempered AP and allowed OP to occur for a longer duration over a diel cycle. The lack of cyanobacterial DOC supply to SRB during AP therefore maximized O2 export. This mechanism is unique to benthic ecosystems because transitions between metabolisms occur on the same time scale as solute transport to functionally distinct layers, with the rearrangement of the system by migration of microorganisms exaggerating the effect. Overall, cyanobacterial versatility disrupts the synergistic relationship between sulfide production and AP, and thus enhances diel O2 production.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev , info:eu-repo/semantics/article
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    ARTIKEL (OA)
  • 3
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    Phototrophic Biofilm Activity and Dynamics of Diurnal Cd Cycling in a Freshwater Stream (2009)
    In:  EPIC3Environmental Science & Technology, 43(19), pp. 7245-7251, ISSN: 0013-936X
    Details
    Publikationsdatum: 2017-03-10
    Beschreibung: Diel cycles of dissolved cationic metal concentrations commonly occur in freshwater streams in apparent response to coincident cycles in water quality parameters (pH, O2, temperature). Hourly sampling of the Cd-contaminated Riou Mort (France) revealed large diel cycles in “total” dissolved Cd (232−357 nM; 〈0.45 μm) and “truly” dissolved Cd (56−297 nM; 〈0.02 μm) which were strongly correlated with changes in water pH. Using measured fluxes, a dissolved O2 model was constructed that indicated that benthic metabolic activities, respiration and photosynthesis, were responsible for the diel O2 (and thus, CO2 and pH) variation in the stream. However, microsensor measurements also showed that the pH changes occurred at the biofilm interface earlier than in the bulk water column. This difference in timing was reflected in the Cd dynamics, where pH-controlled sorption effects caused Cd partitioning from the truly dissolved pool onto the biofilm in the morning, and from the truly dissolved pool onto large colloids (0.02−0.45 μm) later in the day. Because this process causes large changes in the bioavailable Cd fraction, it has significant implications for Cd toxicity in freshwater streams. This study demonstrates the profound control of benthic microbiological processes on the cycling of heavy metals in aquatic systems.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
  • 4
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    Microbial and Chemical Characterization of Underwater Fresh Water Springs in the Dead Sea (2018)
    Details
    Publikationsdatum: 2021-03-29
    Beschreibung: Due to its extreme salinity and high Mg concentration the Dead Sea is characterized by a very low density of cells most of which are Archaea. We discovered several underwater fresh to brackish water springs in the Dead Sea harboring dense microbial communities. We provide the first characterization of these communities, discuss their possible origin, hydrochemical environment, energetic resources and the putative biogeochemical pathways they are mediating. Pyrosequencing of the 16S rRNA gene and community fingerprinting methods showed that the spring community originates from the Dead Sea sediments and not from the aquifer. Furthermore, it suggested that there is a dense Archaeal community in the shoreline pore water of the lake. Sequences of bacterial sulfate reducers, nitrifiers iron oxidizers and iron reducers were identified as well. Analysis of white and green biofilms suggested that sulfide oxidation through chemolitotrophy and phototrophy is highly significant. Hyperspectral analysis showed a tight association between abundant green sulfur bacteria and cyanobacteria in the green biofilms. Together, our findings show that the Dead Sea floor harbors diverse microbial communities, part of which is not known from other hypersaline environments. Analysis of the water’s chemistry shows evidence of microbial activity along the path and suggests that the springs supply nitrogen, phosphorus and organic matter to the microbial communities in the Dead Sea. The underwater springs are a newly recognized water source for the Dead Sea. Their input of microorganisms and nutrients needs to be considered in the assessment of possible impact of dilution events of the lake surface waters, such as those that will occur in the future due to the intended establishment of the Red Sea - Dead Sea water conduit.
    Schlagwort(e): Dead Sea; Archaeal community ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
    Format: 21
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    CITATION GEO-LEO
  • 5
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    Oxygenic photosynthesis as a protection mechanism for cyanobacteria against iron-encrustation in environments with high Fe(2+) concentrations. (2018)
    Details
    Publikationsdatum: 2021-03-29
    Schlagwort(e): oxygenicphototrophs;Cyanobacteria;Fe(II);iron-encrustation;bandedironformations;oxygen microgradients;pHmicrogradients ; 551
    Sprache: Englisch , Englisch
    Materialart: article , publishedVersion
    Standort Signatur Einschränkungen Verfügbarkeit
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    CITATION GEO-LEO
  • 6
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    Oxygen budgets in subtidal arctic (Kongsfjorden, Svalbard) and temperate (Helgoland, North Sea) microphytobenthic communities (2014)
    Inter-Research
    In:  EPIC3Marine Ecology Progress Series, Inter-Research, 504, pp. 27-42, ISSN: 0171-8630
    Details
    Publikationsdatum: 2019-07-16
    Beschreibung: We compared primary production and respiration of temperate (Helgoland, North Sea) and subtidal Arctic (Kongsfjorden, Svalbard) microphytobenthic communities during summer. The diatom communities were generally characterized as cosmopolitan, displayed no site specificity, and had similar chl a and fucoxanthin concentrations. Their net and gross photosynthesis rates and light adaptation intensities, derived from laboratory microsensor measurements, were also similar, despite differences in water temperature. Daily oxygen fluxes across the sediment− water interface were estimated by combining laboratory microprofile and planar optode measurements with in situ data on oxygen penetration and light dynamics. During the study period, the Svalbard sediments were on average net heterotrophic,while the Helgoland sediments were net autotrophic (−22.4 vs. 9.2 mmol O2 m−2 d−1). This was due to high infaunal abundance in the Svalbard sediments that caused high oxygen uptake rates in the sediments and consumption below the sediment euphotic zone. Additionally, bioirrigation of the sediment due to infaunal burrow ventilation was reduced by light; thus, the sedimentary oxygen inventory was reduced with increasing light. Conversely, light-enhanced the oxygen inventory in the Helgoland sediments. Oxygen dynamics in the Svalbard sediments were therefore dominated by bioirrigation, whereas in the Helgoland sediments they were dominated by photosynthetic oxygen production.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
  • 7
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    Hyperspectral imaging of the microscale distribution and dynamics of microphytobenthos in intertidal sediments (2013)
    In:  EPIC3Limnology and Oceanography: Methods, 11(10), pp. 511-528, ISSN: 15415856
    Details
    Publikationsdatum: 2017-02-01
    Beschreibung: We describe a novel, field-deployable hyperspectral imaging system, called Hypersub, that allows noninvasive in situ mapping of the microphytobenthos (MPB) biomass distribution with a high spatial (sub-millimeter) and temporal (minutes) resolution over areas of 1 × 1 m. The biomass is derived from a log-transformed and near-infrared corrected reflectance hyperspectral index, which exhibits a linear relationship (R2 〉 0.97) with the chlorophyll a (Chl a) concentration in the euphotic zone of the sediment and depends on the sediment grain size. Deployments of the system revealed that due to factors such as sediment topography, bioturbation, and grazing, the distribution of MPB in intertidal sediments is remarkably heterogeneous, with Chl a concentrations varying laterally by up to 400% of the average value over a distance of 1 cm. Furthermore, due to tidal cycling and diel light variability, MPB concentrations in the top 1 mm of sediments are very dynamic, changing by 40–80% over a few hours due to vertical migration. We argue that the high-resolution hyperspectral imaging method overcomes the inadequate resolution of traditional methods based on sedimentary Chl a extraction, and thus helps improve our understanding of the processes that control benthic primary production in coastal sediments.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , peerRev
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
  • 8
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    Microsensor measurements in photosynthetic microbial mats (2012)
    PANGAEA
    In:  Max-Planck-Institut für Marine Mikrobiologie | Supplement to: Al-Najjar, Mohammad A A; de Beer, Dirk; Kühl, Michael; Polerecky, Lubos (2012): Light utilization efficiency in photosynthetic microbial mats. Environmental Microbiology, 14(4), 982-992, https://doi.org/10.1111/j.1462-2920.2011.02676.x
    Details
    Publikationsdatum: 2023-01-13
    Beschreibung: Based on combined microsensor measurements of irradiance, temperature and O2, we compared light energy budgets in photosynthetic microbial mats, with a special focus on the efficiency of light energy conservation by photosynthesis. The euphotic zones in the three studied mats differed in their phototrophic community structure, pigment concentrations and thickness. In all mats, 〈 1% of the absorbed light energy was conserved via photosynthesis at high incident irradiance, while the rest was dissipated as heat. Under light-limiting conditions, the photosynthetic efficiency reached a maximum, which varied among the studied mats between 4.5% and 16.2% and was significantly lower than the theoretical maximum of 27.7%. The maximum efficiency correlated linearly with the light attenuation coefficient and photopigment concentration in the euphotic zone. Higher photosynthetic efficiency was found in mats with a thinner and more densely populated euphotic zone. Microbial mats exhibit a lower photosynthetic efficiency compared with ecosystems with a more open canopy-like organization of photosynthetic elements, where light propagation is not hindered to the same extent by photosynthetically inactive components; such components contributed about 40-80% to light absorption in the investigated microbial mats, which is in a similar range as in oceanic planktonic systems.
    Materialart: Dataset
    Format: application/zip, 6 datasets
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 9
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    Chlorophyll and true-color maps of sediments from the intertidal zones in Winyah Bay, South Carolina, USA and List, Sylt, Germany (2015)
    PANGAEA
    In:  Supplement to: Chennu, Arjun; Volkenborn, Nils; de Beer, Dirk; Wethey, David S; Woodin, Sarah A; Polerecky, Lubos (2015): Effects of bioadvection by Arenicola marina on microphytobenthos in permeable sediments. PLoS ONE, 10(7), e0134236, https://doi.org/10.1371/journal.pone.0134236
    Details
    Publikationsdatum: 2023-01-13
    Beschreibung: We used hyperspectral imaging to study short-term effects of bioturbation by lugworms (Arenicola marina) on the surficial biomass of microphytobenthos (MPB) in permeable marine sediments. Within days to weeks after the addition of a lugworm to a homogenized and recomposed sediment, the average surficial MPB biomass and its spatial heterogeneity were, respectively, 150 - 250% and 280% higher than in sediments without lugworms. The surficial sediment area impacted by a single medium-sized lugworm (~4 g wet weight) over this time-scale was at least 340 cm**2. While sediment reworking was the primary cause of the increased spatial heterogeneity, experiments with lugworm-mimics together with modeling showed that bioadvective porewater transport from depth to the sediment surface, as induced by the lugworm ventilating its burrow, was the main cause of the increased surficial MPB biomass. Although direct measurements of nutrient fluxes are lacking, our present data show that enhanced advective supply of nutrients from deeper sediment layers induced by faunal ventilation is an important mechanism that fuels high primary productivity at the surface of permeable sediments even though these systems are generally characterized by low standing stocks of nutrients and organic material.
    Materialart: Dataset
    Format: application/zip, 2 datasets
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 10
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    Benthic cyanobacterial mat (BCM) abundance on samples from the coast of Curacao (2015)
    PANGAEA
    In:  Supplement to: Brocke, Hannah J; Polerecky, Lubos; de Beer, Dirk; Weber, Miriam; Claudet, Joachim; Nugues, Maggy M (2015): Organic Matter Degradation Drives Benthic Cyanobacterial Mat Abundance on Caribbean Coral Reefs. PLoS ONE, 10(5), e0125445, https://doi.org/10.1371/journal.pone.0125445
    Details
    Publikationsdatum: 2023-01-14
    Beschreibung: Benthic cyanobacterial mats (BCMs) are impacting coral reefs worldwide. However, the factors and mechanisms driving their proliferation are unclear. We conducted a multi-year survey around the Caribbean island of Curaçao, which revealed highest BCM abundance on sheltered reefs close to urbanised areas. Reefs with high BCM abundance were also characterised by high benthic cover of macroalgae and low cover of corals. Nutrient concentrations in the water-column were consistently low, but markedly increased just above substrata (both sandy and hard) covered with BCMs. This was true for sites with both high and low BCM coverage, suggesting that BCM growth is stimulated by a localised, substrate-linked release of nutrients from the microbial degradation of organic matter. This hypothesis was supported by a higher organic content in sediments on reefs with high BCM coverage, and by an in situ experiment which showed that BCMs grew within days on sediments enriched with organic matter (Spirulina). We propose that nutrient runoff from urbanised areas stimulates phototrophic blooms and enhances organic matter concentrations on the reef. This organic matter is transported by currents and settles on the seabed at sites with low hydrodynamics. Subsequently, nutrients released from the organic matter degradation fuel the growth of BCMs. Improved management of nutrients generated on land should lower organic loading of sediments and other benthos (e.g. turf and macroalgae) to reduce BCM proliferation on coral reefs.
    Materialart: Dataset
    Format: application/zip, 7 datasets
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
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